The exemplary embodiment relates to an edge contrast adjustment filter. While it is particularly directed to the art of digital image processing, and will be thus described with specific reference thereto, it will be appreciated that the exemplary embodiment may have usefulness in other fields and applications.
By way of background, for fine text and line objects, sharpness is the single most important attribute for evaluation of image quality. To preserve the quality of edges, approaches using a tagging system enable the edge pixels of an object to use high addressability halftones when the object is surrounded by a white background. When an object overlaps the white background and a light tint background, the tagging system sometimes fails to identify the edge for the portion over the tint background, and, therefore, fails to render the edge with the high addressability halftones. This results in an inconsistent edge quality, as the text/line will appear sharp over the white and blurry over the tint background.
These problems have been associated with text/line objects that overlap both paper white and a light tint background. Because the outlining feature in the contone rendering module (CRM), as described in U.S. Pat. No. 6,243,499, is threshold-based, there are cases where the outlining will be disabled for the portions of these objects over the tint, resulting in sub-optimal image quality as shown in FIG. 1. Clearly, the sharpness of the text/line over the tint is severely degraded, and it would be desirable to maintain an approximately uniform object quality in these cases.
The exemplary embodiment contemplates a new and improved method and apparatus that resolve the above-referenced difficulties and others.